Method of producing uranium



lVIETHOD F PRODUCING URANIUM Laurence S. Foster, Belmont, and Theodore T. Magel, Cambridge, Mass, assignors to the United States of America as represented by the United States Atomic Energy Commission No Drawing. Application June 10, 1946 Serial No. 675,834

Claims. (Cl. 7584.1)

This invention is directed to the production of uranium in metallic form. In the reaction of uranium halides, such as uranium tetrafiuoride or other tetrahalide, with a reducing metal, the yield of uranium metal may be considerably below the theoretical. This is particularly true when small charges of reaction mixture are used. This process normally is conducted under conditions such that molten uranium metal and molten reducing metal halide (slag) are formed and the metal is allowed to separate from the reducing metal halide slag. Apparently the low yields which occasionally are secured result from an incomplete separation of the metal from the slag.

In accordance with the present invention it has been found that improved yields may be secured by simultaneously reducing a uranium halide such as uranium tetrafluoride together with a small amount of a manganese halide such as manganese chloride (MnCl it has been found that by co-reducing a small quantity of the manganese compound with the uranium halide, a metal phase melting at a temperature substantially below the melting point of pure uranium is secured, and it seems probable that the improved yields are due to the fact that less heat is required to maintain the metal in molten state and therefore that the phases (molten metal and slag) remain in liquid state for a longer period of time thus premitting a more complete separation thereof.

The process is particularly advantageous where the production of uranium metal is in small amounts, for example grams or less. However, it may be applied generally to the production of a metallic uranium composition in large or small quantity and otters the advantage that less heat must be introduced into the reaction mixture or developed therein thanotherwise would be required. Moreover if desired the operation may be conducted at a temperature below the melting point of uranium thereby reducing the attack of the metal upon refractory liners and reactors.

The reaction may be conveniently conducted in a metallic bomb which may be lined with a suitable refractory capable of withstanding the attack of molten metal or other reactants at the temperature of operation. Beryllium oxide or alkaline earth oxides such as calcium oxide or calcined dolomite are suitable for this purpose.

In the operation of the process, the reaction mixture may comprise uranium tetrafiuoride or other uranium tetrahalide, manganese dichloride or other manganese halide and a reducing metal above uranium and manganese in the electromotive series. Suitable reducing metals for this purpose include the alkali metals and alkaline earth metals such as sodium, lithium, potassium, calcium, barium, strontium and magnesium. The halides preferably should be in finely divided state generally having a particle size of about minus 50 to minus 300 mesh. The reducing metal should be in pulverulent form, and in general the halides and reducing metal should be thoroughly intermixed. The reactants preferably should be anhydrous.

The amount of reducing metal used is, in most cases,

2,834,672 Patented May13, 1958 somewhat in excess (5 to 10 percent or more) of the amount of reducing agent theoretically required to reduce the two halides and form metal. The amount of manganese halide used will depend upon the concentration of manganese desired or permissible in the uranium composition, since, in general, the ratio of manganese to uranium in the metal composition will not substantially differ from the ratio of manganese halide to uranium halide in terms of moles of halides used. Manganeseuranium compositions having a melting point below that of uranium metal should be produced and the amount of manganese halide should be adjusted to this end. In general the amount of uranium should exceed the amount of manganese in the composition and usually amounts of the order of one to 10 percent of manganese (in the form of halide) based upon the weight of uranium to be reduced, should be used. This amount of manganese can be varied more widely, however, since uranium-manganese alloys which contain manganese up to about 60 atomic percent have melting points below that of pure uranium.

After the reaction mixture has been introduced into the bomb, the bomb is closed and the reaction is initiated. Reaction initiation may be effected by heating the reaction mixture to approximately 400 to 800 C. Upon such heating, reaction takes place with evolution of heat and where the reaction is carried on upon a substantial scale the added heat together with the evolved heat of reaction is sutlicient' to cause formation of the uranium manganese composition in molten state. This molten metal composition then settles away from the reducingmetalhalide slag and may be drained off in molten state, or the resulting product may be allowed to solidify whereby a billet of metallic uranium-manganese alloy is secured.

At all events, sufiicient heat must be available to maintain the reaction mass in molten state until the metal composition and the slag have separated substantially completely. Where the reaction is conducted on a large scale (sufficient to form 20 to pounds or more of uranium metal composition) and where calcium is used as the reducing metal, suificient heat is evolved by the reaction to develop the required temperature. If the reactor utilized is sufiiciently insulated that heat losses are not excessive, the reaction mass will remain molten for the required period of time to permit the separation to occur. In this case, reaction may be initiated simply by an electrical fuse or resistance wire. On the other hand, where the reaction is carried out on a small scale, for example with one or several'grams, or where the reaction is conducted using other reducing metals such as magnesium, additional heat must be introduced into the reaction mixture. This heat may be introduced by preheating thereactants, by use of an induction-heated bomb and/ or by conducting an auxiliary exothermic reaction within the reaction mixture. For example, iodine or potassium chlorate may be incorporated in the reaction mixture and the amount of calcium or reducing metal increased accordingly, and the heat evolved from the reaction of the reducing metal with the iodine or potassium chlorate or other booster will serve to establish and maintain the required temperature.

Where the process is conducted on a very small scale, some difiiculty may be encountered in obtaining substantially complete separation of the phases. This separation may be facilitated by centrifuging the reaction mixture during reaction. Such a process is described in an application for United States Letters Patent of Theodore T. Magel, Serial No. 584,684, filed March 24, 1945, and all disclosure in such application and not inconsistent with the disclosure of the present application is hereby incorporated'herein reference. The following example is illustrative. v

Example 1 v Uranium tetrafluoride, manganese chloride, iodine and calcium metal were mixed in the proportion of 1.17 grams of MnCl 3.33 grams of iodine, 5.44 grams of calcium metal and 13.3 grams of UF to form an essentially uniform mixture. This mixture was placed in a small bomb lined with electrically fused dolomite, and the bomb was heated in an electric induction furnace to a temperature of about 700 to 800 C. This temperature was maintained for about 45 minutes, and thereafter the bomb was permitted to cool- Upon opening the bomb, there was found that the uranium-manganese composition had settled almost completely away from the slag and that the billet or button of uranium-manganese metal contained approximately 98 percent of the uranium introduced as the tetrafluoride. In contrast, when this process was performed on the same scale using no manganese, only about 55 to 80 percent of the uranium was recovered.

While the invention has been described with particular reference to the production of metal from uranium tetrafluoride, it is not limited thereto but may be applied to the production of uranium metal from uranium tetrachloride, uranium .tetrabromide, uranium tetraiodide, uranium trichloride or uranium tribromide. Likewise, the manganese halide used may be manganese trichloride, or the corresponding difluoride, trifluoride, dibromide, diiodide, etc., may be used in lieu of manganese dichloride. 7

The product obtained is a uranium-manganese alloy which has a melting point below that of pure uranium.

This uranium composition may be used as such or it may be treated to remove the manganese. For example, the manganese may be distilled from the uranium metal by heating in vacuo for a substantial period of time at a temperature above the melting point of uranium (about 1100 C.) but below the temperature at which substantial vaporization of uranium tends to occur. The uranium metal which remains behind in such a process may be secured in a relatively pure state. In accordance with a further modification, the process can be used in the reduction of other uranium compounds to form a metallic uranium composition. Thus uranium oxide (U0 or U 0 may be reduced with alkali or alkaline earth metals together with manganese halides or manganese oxides such as manganese dioxide at a temperature suificiently high to form the manganese-uranium metal composition in molten state, and this molten metal composition maythen be separated from the resulting slag as herein contemplated. Numerous other modifications of the invention are permissible as will be understood by those skilled in the art.

Although the present invention has been described with reference to the specific details of certain embodiments thereof, it is not intended that such details shall be regarded as'limitations upon the scope of the invention except insofar as included in the accompanying claims.

What is claimed is: i 1. A process for the production of uranium metal, which comprises heating a closed system containing a mixture comprising a uranium halide, a manganese halide and at least one metal selected from the group consisting of alkali and alkaline earth metals to a temperature between 400 and 800 C. wherein the manganese halide is present in stoichiometric proportions equivalent to a yield of uranium-manganese alloy containing from 1 to 60 atomic percent of manganese; maintaining said temperature until the reduction of uranium and manganese is completed and molten metal is obtained; holding the resultant reaction products in said heated closed system for a suificient length of time to allow settling of the molten uranium-manganese alloy; separating said alloy from the slag formed; and recovering the uranium from said uranium-manganese alloy.

2. The process of claim lwherein the uranium halide is uranium tetrafluoride and the manganese halide is manganese dichloride.

3. The process of claim 1 wherein the reducing metal is calcium.

4. A process for the production of uranium metal,

which comprises heating a closed system containing a mixture comprising a uranium halide, a manganese halide and at least one metal selected from the group consisting of alkali and alkaline earth metals to a temperature between 400 and 800 C. wherein the manganese halide is present in stoichiometric proportions equivalent to a yield of uranium-manganese alloy containing from 1 to 60 atomic percent of manganese; maintaining said temperature until the reduction of uranium and manganese is completed and molten metal is obtained; holding the resultant reaction products in said heated closed system for a sufiicient length of time to allow settling of the molten uranium-manganese alloy; separating said alloy from the slag formed; and recovering said uranium from said uranium-manganese alloy by distilling of the manganese at reduced pressure at a temperature above the melting point of uranium and below the boiling point of uranium.

5. A process for the production of uranium metal, comprising heating a closed system containing 'a mixture consisting of 1.17 parts by weight of manganese dichloride, 13.3 parts by weight of uranium tetrafluoride, 5.44 parts by weight of calcium and 3.33 parts by weight of iodine to a temperature of about from 700 to 800 C,; maintaining said temperature for about forty-five minutes whereby a uranium-manganese alloy separates and settles from a slag phase; cooling the reaction products obtained; removing said uranium-manganese alloy from said slag; and distilling said manganese from said uranium at reduced pressure and a temperature of approximately 1100 C.

References Cited in the file of this patent UNITED STATES PATENTS 489,303 Greene etal. Jan. 3, 1893 1,088,909 Kuzel Mar. 3, 1914 1,151,160 Brown Aug. 24, 1915 1,321,684 Turner et a1. Nov. 11, 1919 1,568,685 Moore Jan. 5, 1926 1,728,940 Marden Sept. 24, 1929 FOREIGN PATENTS 258,024 Great Britain Sept. 16, 1926 OTHER REFERENCES Mellor: Comprehensive Treatise of Inorganic and Theoretical Chemistry, vol. 12, pages 15 and 172 (1932). Published by Longmans, Green & Co., London. 

1. A PROCESS FOR THE PRODUCTION OF URANIUM METAL, WHICH COMPRISES HEATING A CLOSED SYSTEM CONTAINING A MIXTURE COMPRISING A URANIUM HALIDE, A MANGANESE HALIDE AND AT LEAST ONE METAL SELECTED FROM THE GROUP CONSISTING OF ALKALI AND ALKALINE EARTH METALS TO A TEMPERATURE BETWEEN 400* AND 800*C. WHEREIN THE MANGANESE HALIDE IS PRESENT IN STOICHIOMETRIC PROPORTIONS EQUIVALENT TO A YIELD OF URANIUM-MANGANESE ALLOY CONTAINING FROM 1 TO 60 ATOMIC PERCENT OF MANGANESE, MAINTAINING SAID TEMPERATURE UNTIL THE REDUCTION OFURANIUM AND MANGANESE IS COMPLETED AND MOLTEN METAL IS OBTAINED, HOLDING THE RESULTANT REACTION PRODUCTS IN SAID HEATED CLOSED SYSTEM FOR A SUFFICIENT LENGTH OF TIME TO ALLOW SETTLING OF THE MOLTEN URANIUM-MANGANESE ALLOY, SEPARATING SAID ALLOY FROM THE SLAG FORMED, AND RECOVERING THE URANIUM FROM SAID URANIUM-MANGANESE ALLOY. 